JP6679072B2 - Resin composition and hydrolysis method thereof - Google Patents

Description

  The present invention relates to a resin composition having excellent hydrolyzability and a hydrolysis method thereof.

In recent years, along with the deterioration of the global environment, there is an increasing interest in resin recycling and additives that are safe for the living body and have a low impact on the global environment. Resins represented by polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL) and the like are used as biodegradable resins that are decomposed by water or enzymes in a natural environment or in a living body.
For example, PLA is used for applications such as disposable containers and packaging materials because it has good workability and excellent mechanical strength of molded products. However, PLA has a problem that the hydrolysis rate is slower than that of PGA or PCL.

  In order to overcome such problems of PLA, as a method of improving the hydrolysis rate of PLA, for example, a method of blending PLA with a hydrophilic additive such as polyethylene glycol has been proposed. However, PLA has a low hydrophilicity and is difficult to be compatible with hydrophilic substances such as polyethylene glycol, so that the hydrophilic additive may bleed out during or after molding (bleed-out), resulting in a decrease in mechanical strength of the molded product. Or, the appearance such as transparency is impaired, which is not practical.

Regarding hydrolysis of PLA, acid and alkaline hydrolysis have been reported (Non-patent Documents 1 and 2).
The present applicant has proposed to add a copolymer that promotes hydrolysis to PLA (Patent Documents 1 and 2).

International Publication 2012/137681 Pamphlet International publication 2014/038608 pamphlet

"Properties and Morphology of Poly (L-lactide) .II. Hydrolysis in Alkaline Solution", Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 36, 59-66 (1998) ”Poly (L-lactide). IX. Hydrolysis in Acid Media”, Journal of Applied Polymer Science, Vol. 86, 186-194 (2002)

  In Non-Patent Documents 1 and 2, PLA films are annealed to prepare samples having different crystallinity, and the hydrolysis behavior thereof is confirmed. According to Non-Patent Document 1, it is considered that the PLA film is decomposed due to the erosion of the amorphous portion on the film surface. The higher the crystallinity, the less the weight loss due to the decomposition, that is, the more difficult the hydrolysis is. Is shown. Non-Patent Document 2 further investigates the difference in hydrolysis between acidic, neutral, and alkaline, and shows that the alkaline (pH 12) hydrolysis is higher than neutral and acidic. Similar to Non-Patent Document 1, it has been shown that the sample with high crystallinity has a slower rate of weight loss, whereas the sample with high crystallinity has a faster decrease in molecular weight. However, in each case, a long period of about 200 days is required for complete decomposition. That is, although PLA usually has higher heat resistance and mechanical strength due to crystallization, hydrolysis slows down as compared with the case where crystallization does not cause crystallization. Therefore, in order to increase the decomposition rate, it is necessary to lower the crystallinity and sacrifice heat resistance and mechanical strength, and it has been difficult to achieve both hydrolysis rate and heat resistance and mechanical strength.

  Patent Documents 1 and 2 show that the addition of the copolymer (hydrolysis accelerator) improves the hydrolysis rate. In both cases, hydrolyzability at 50 ° C. to 80 ° C. under almost neutral conditions such as distilled water and ion-exchanged water has been investigated, and lower temperature conditions and dependence on crystallinity have not been investigated.

  As described above, if both improvement of heat resistance and mechanical strength by crystallization and improvement of hydrolysis rate can be achieved at the same time, hydrolysis at low temperatures that could not be used until now, heat resistance and mechanical properties such as sterilization treatment, etc. It can be used under high temperature and high pressure conditions that require strength.

  An object of the present invention is to provide a resin composition that can be rapidly hydrolyzed and a hydrolysis method.

  By increasing the crystallinity of a resin composition in which a crystalline polymer having hydrolyzability is combined with a hydrolysis accelerator, the inventors of the present invention contradicted the conventional teaching, and thus hydrolyzed, particularly in an alkaline aqueous solution. It was found that the hydrolysis rate was significantly increased.

That is, one embodiment of the present invention is a resin composition containing a crystalline polymer (A) having a hydrolyzability and a hydrolysis accelerator (B), wherein the resin composition has a crystallinity of 15 % Or more and 60% or less, relates to the resin composition (C).
Moreover, one form of this invention is a hydrolysis method of the said resin composition (C), Comprising: It hydrolyzes in the aqueous solution whose pH is more than 7, The hydrolysis method characterized by the above-mentioned.

  According to the present invention, a resin composition having excellent heat resistance and mechanical strength and having improved hydrolyzability can be provided. Further, the hydrolysis method according to the present invention can hydrolyze the resin composition in an extremely short period of time.

<Crystalline Polymer (A) Having Hydrolyzability>
The hydrolyzable crystalline polymer (A) used in the present invention (hereinafter, simply referred to as “crystalline polymer (A)”) is not particularly limited as long as it is a hydrolyzable crystalline polymer. Examples thereof include polyesters, and in particular, aliphatic polyester resins composed of polyhydroxycarboxylic acid, diol and dicarboxylic acid can be used.

  In the present invention, the polyhydroxycarboxylic acid means a polymer or copolymer having a repeating unit (constitutional unit) (a-1) derived from a hydroxycarboxylic acid having both a hydroxyl group and a carboxyl group.

  Specific examples of the hydroxycarboxylic acid include lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methyl. Butyric acid, 2-methyl lactic acid, 2-hydroxyvaleric acid, 2-hydroxycaproic acid, 2-hydroxylauric acid, 2-hydroxymyristic acid, 2-hydroxypalmitic acid, 2-hydroxystearic acid, malic acid, citric acid, tartaric acid Ring-opening products of lactones such as 2-hydroxy-3-methylbutyric acid, 2-cyclohexyl-2-hydroxyacetic acid, mandelic acid, salicylic acid, and caprolactone. You may use these 2 or more types in mixture.

  The polyhydroxycarboxylic acid may have a structural unit (copolymerization component) other than the hydroxycarboxylic acid as long as the hydrolyzability is not significantly impaired. However, in 100 mol% of all the structural units of the polyhydroxycarboxylic acid. The constituent unit (a-1) derived from a hydroxycarboxylic acid is preferably 20 mol% or more, more preferably 50 mol% or more, and particularly preferably 100%.

  Among the polyhydroxycarboxylic acids, from the viewpoint of compatibility with the hydrolysis accelerator (B), a polymer or copolymer in which the hydroxycarboxylic acid is lactic acid is preferable, and polylactic acid (homopolymer) is more preferable. Polylactic acid may be one synthesized from lactic acid as a starting material or one synthesized from lactide as a starting material.

  In the present invention, the aliphatic polyester resin composed of a diol and a dicarboxylic acid means a polymer or a copolymer having a repeating unit (constitutional unit) derived from the diol and the dicarboxylic acid. The aliphatic polyester resin may have a constitutional unit (copolymerization component) other than the constitutional unit derived from the diol and the dicarboxylic acid, as long as the hydrolyzability as the crystalline polymer (A) is not significantly impaired. Good.

  Specific examples of the aliphatic polyester resin comprising diol and dicarboxylic acid include polyethylene succinate, polyethylene adipate, polyethylene sebacate, polydiethylene succinate, polydiethylene adipate, polyethylene succinate adipate, polydiethylene sebacate, polybutylene succinate. , Polybutylene adipate, polybutylene succinate adipate, and polybutylene sebacate.

  The molecular weight of the crystalline polymer (A) is not particularly limited, but one having a larger molecular weight than the hydrolysis accelerator (B) is preferable. Considering the ease of mixing with the hydrolysis accelerator (B), the weight average molecular weight of the crystalline polymer (A) is preferably 2,000 to 2,000,000, more preferably 3,000 to 1 , 000,000, particularly preferably more than 50,000 and not more than 500,000. This weight average molecular weight is a value determined by gel permeation chromatography (GPC) under the conditions described in the examples below.

<Hydrolysis accelerator (B)>
As the hydrolysis accelerator (B) used in the present invention, any one can be used as long as it promotes the hydrolyzability of the crystalline polymer (A), and particularly, a structural unit (a) derived from a hydroxycarboxylic acid. -2) and a copolymer having a structural unit (b-1) derived from a polycarboxylic acid are preferred. The "constitutional unit" is a unit derived from a polymerizable monomer and does not include a terminal group. The hydrolysis accelerator (B) may be any of a random copolymer, a block copolymer and a graft copolymer. Examples of the constitutional unit (a-2) derived from the hydroxycarboxylic acid include those exemplified as the constitutional unit (a-1) derived from the hydroxycarboxylic acid constituting the crystalline polymer (A), and a crystalline polymer to be combined. It is preferable to use the same one as the structural unit (a-1) of (A). Particularly, the structural unit (a-2) derived from hydroxycarboxylic acid is preferably a unit derived from lactic acid.

  The structural unit (b-1) is not particularly limited as long as it is a structural unit derived from a polycarboxylic acid. The polyvalent carboxylic acid is preferably one or more selected from divalent or trivalent polycarboxylic acids, and among them, aminodicarboxylic acid, hydroxydicarboxylic acid and hydroxytricarboxylic acid are more preferable, aspartic acid, glutamic acid, Particularly preferred is at least one selected from malic acid, citric acid and tartaric acid. These polyvalent carboxylic acids may have one kind or two or more different kinds. The structural unit derived from a polyvalent carboxylic acid may form a ring structure such as an imide ring, the ring structure may be ring-opened, or these ring structures and ring-opened structures are mixed. Or two or more different ring structures and / or ring-opening structures may be included.

  The hydrolysis accelerator (B) is not particularly limited as long as it is a copolymer having the structural unit (a-2) and the structural unit (b-1) described above. Of these, aspartic acid-lactic acid copolymer, malic acid-lactic acid copolymer, and citric acid-lactic acid copolymer are particularly preferable.

  The molar composition ratio [(a-2) / (b-1)] of the structural unit (a-2) and the structural unit (b-1) in the hydrolysis accelerator (B) is preferably the charged amount at the time of polymerization. Is 1/1 to 50/1, more preferably 10/1 to 20/1. When the molar composition ratio is within these ranges, a copolymer having an excellent effect of promoting the decomposition rate and an excellent compatibility with the crystalline polymer (A) can be obtained.

  In the hydrolysis accelerator (B), constitutional units other than the constitutional units (a-2) and (b-1) (units derived from other copolymerization components) may be present. However, its amount must be such that the properties of the hydrolysis accelerator (B) are not significantly impaired. From this point, it is desirable that the amount of the other structural unit is about 20 mol% or less in 100 mol% of the entire structural units of the hydrolysis accelerator (B).

  The weight average molecular weight of the hydrolysis accelerator (B) is 1,000 or more and 50,000 or less, preferably 2,500 or more and 30,000 or less, and particularly preferably in the range of 2,500 to 10,000. It is within. This weight average molecular weight is a value determined by gel permeation chromatography (GPC) under the conditions described in the examples below.

  The method for producing the hydrolysis accelerator (B) is not particularly limited. Generally, it can be obtained by mixing a polycarboxylic acid and a hydroxycarboxylic acid in a desired ratio and dehydrating and polycondensing under heating and reduced pressure in the presence or absence of a catalyst. It can also be obtained by reacting an anhydride cyclic compound of hydroxycarboxylic acid such as lactide, glycolide, or caprolactone with a polyvalent carboxylic acid.

<Resin composition (C)>
The resin composition (C) according to the present invention is obtained by mixing the crystalline polymer (A) and the hydrolysis accelerator (B). The mass composition ratio [(A) / (B)] is 95/5 to 50/50, preferably 95 /, with the total amount of the crystalline polymer (A) and the hydrolysis accelerator (B) being 100. It is 5 to 55/45, more preferably 95/5 to 60/40, and particularly preferably 95/5 to 80/20. When the mass composition ratio is within these ranges, the hydrolysis rate promoting effect of the hydrolysis accelerator (B) is exhibited while maintaining the properties of the crystalline polymer (A), which is preferable. Further, the larger the amount of the hydrolysis accelerator (B), the more the decomposition rate of the resin composition (C) can be obtained. On the other hand, if the mass composition ratio is more than 95/5, the decomposition promoting effect by the addition of the hydrolysis accelerator (B) is not sufficient, and if it is less than 50/50, the crystallinity of the resin composition (C) is large. In addition, the crystalline polymer (A) is unfavorable because it impairs the properties of the crystalline polymer (A).

  The method for mixing the hydrolysis accelerator (B) with the crystalline polymer (A) is not particularly limited. Preferably, both are melt-kneaded or dissolved in a solvent and mixed by stirring. By such a production method, a uniform resin composition (C) can be obtained from the crystalline polymer (A) and the hydrolysis accelerator (B).

  The resin composition (C) is an addition that can be added to a polymer other than the hydrolysis accelerator (B) and the crystalline polymer (A) or an ordinary resin, as long as the properties of the crystalline polymer (A) are not significantly impaired. The agent may be included.

The crystallinity of the resin composition (C) is 15% or more and 60% or less. The crystallinity referred to in the present invention is obtained as a function of the enthalpy of fusion, enthalpy of crystallization, and enthalpy of recrystallization obtained by differential thermal analysis (DSC), as will be shown in Examples described later. From the viewpoint of heat resistance, the lower limit of crystallinity is preferably 20%, more preferably 25%. The upper limit of the crystallinity is preferably 55%, more preferably 50% from the viewpoint of heat resistance and simplification of the crystallization process. When the crystallinity is less than 15%, not only the effect of improving the heat resistance of the resin composition (C) due to crystallization is small, but also only the effect of adding the hydrolysis accelerator (B) is exhibited, and crystallization and hydrolysis A synergistic effect with the addition of the accelerator (B) does not appear. A crystallinity of more than 60% requires a long crystallization step, and a crystallinity of more than 60% makes it difficult to hydrolyze due to a decrease in an amorphous region.
The crystallinity can be adjusted by a known method, such as a method of adjusting a heating temperature, a temperature rising rate, a cooling rate, etc. at the time of molding of a molded article using the resin composition (C), or crystallization of the molded article. Examples include a method of reheating (annealing) at a temperature equal to or higher than the melting temperature and lower than the melting temperature. Further, a method of using a crystal nucleating agent, a method of increasing the crystallinity by a stretching treatment, and the like are also included. Usually, polylactic acid, which is an example of the crystalline polymer (A), has a slow crystallization rate, and a product obtained by molding a mold and rapidly cooling it has a low crystallinity.

  The molecular weight of the resin composition (C) is not particularly limited. Considering moldability, the weight average molecular weight of the resin composition (C) is preferably 1,000 to 1,000,000, more preferably 5,000 to 500,000, and particularly preferably 50,000 to 300,000. This weight average molecular weight is a value determined by gel permeation chromatography (GPC) under the conditions described in the examples below.

  The resin composition (C) according to the present invention can be molded into various shapes such as a film, a sheet, a fiber and a tablet by a conventionally known molding method.

<Hydrolysis method>
The hydrolysis method according to the present invention is a method of hydrolyzing the above resin composition (C) in an aqueous solution having a pH of more than 7 (referred to as an alkaline aqueous solution). The pH is preferably 7.1 or higher, more preferably 8 or higher. As a preferred embodiment of the aqueous solution, an aqueous solution having an initial pH of more than 7 before immersion in the resin composition (C) can be mentioned. Further, as another embodiment, an aqueous solution having an initial pH of 7 or less and adding and dissolving a basic substance so that the pH after the immersion in the resin composition (C) becomes higher than 7 can be mentioned. In any of the methods, the pH is preferably higher than 7 in most of the decomposition process of the resin composition (C).
Usually, a molded article made of the resin composition (C) is immersed in an alkaline aqueous solution. Moreover, the alkaline aqueous solution can be hydrolyzed by spraying a molded article made of the resin composition (C) with a spray or the like. The temperature of the alkaline aqueous solution is not particularly limited, but is preferably 30 ° C. or higher and lower than the melting point of the resin composition (C). The higher the temperature is, the higher the hydrolysis rate can be. However, the energy cost is correspondingly increased. Therefore, the temperature is appropriately adjusted according to the purpose. The present invention enables faster hydrolysis at a temperature lower than the temperatures examined in Patent Documents 1 and 2. In addition, the resin composition (C) has improved heat resistance by being crystallized, and can be used for applications that require hydrolysis under high temperature and high pressure. In this case, at a hydrolysis temperature above the melting point of the resin composition (C), the resin composition (C) will melt and the effect of adding the decomposition accelerator (B) will be lost. It is necessary to perform hydrolysis at a temperature lower than the melting point of the substance (C).

  The basic substance contained in the alkaline aqueous solution is not particularly limited, but in consideration of versatility and safety, an alkali metal hydroxide is preferable, and sodium hydroxide is more preferable. Further, an inorganic salt or an organic salt may be added to form a buffer solution.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In the examples, "part" indicates part by mass. Each measuring method in the examples is as follows.

<Weight average molecular weight (Mw)>
The sample was dissolved in chloroform (concentration: about 0.5% by mass), and the weight average molecular weight (Mw) was obtained as a polystyrene conversion value by gel permeation chromatography (GPC).
The measurement conditions are shown below.
RI detector: JASCO RI-2031,
Column: SHODEX LF-G and LF-804,
Column temperature: 40 ℃,
Solvent: chloroform,
Flow rate: 1.0 ml / min.

<Crystallinity>
Using a DSC apparatus (DSC Q-200TA manufactured by TA Instrument Co.), a sample of about 4 to 5 mg was measured at a temperature rising rate of 10 ° C./min in a temperature range of 0 ° C. to 200 ° C., and a melting enthalpy (ΔHm) and a crystal were measured. The enthalpy of formation (ΔHc), the enthalpy of recrystallization (ΔHr), the melting point (Tm) and the glass transition temperature (Tg) were determined. The crystallinity (Xc) was calculated by the following formula.
Xc (%) = {(| ΔHm | − | ΔHc | − | ΔHr |) / | ΔHf |} × 100
Here, the enthalpy of fusion (ΔHf) when 100% of polylactic acid was crystallized was set to 93.1 J / g. The crystallinity was expressed as the crystallinity of the entire blend.

<Hydrolysis test>
A sample having a thickness of 0.2 mm and 20 mm square was placed in a glass container, dipped in the following solutions having different pHs, and allowed to stand in a water bath controlled at 40 ° C. The pH was kept constant by replacing the liquid so that the pH did not change during the decomposition. After a predetermined time had elapsed, the sample was collected, washed with distilled water, and then vacuum dried at room temperature for 24 hours, and the mass was measured. The mass retention rate by hydrolysis was calculated by the following formula. When the sample could not be recovered, the mass retention rate was set to 0% assuming that the decomposition of the sample was completed.
When the mass of the sample before the test is W ₀ and the mass of the vacuum dried sample after the test is W _d ,
Mass retention rate (%) = (W _d / W ₀ ) × 100
Solutions with different pH (1) pH 7.4: Phosphate buffer (2) pH 12.0: KCl-NaOH buffer

<Production Example 1> Production of lactic acid-malic acid copolymer (PML) A glass reactor of 500 ml size equipped with a stirrer and a degassing port was placed in Wako Pure Chemical Industries, Ltd. D, L-malic acid 13.4 g (0. 1 mol) and 100.2 g (1.0 mol) of 90% L-lactic acid manufactured by Purac Co. were charged. The reactor was immersed in an oil bath, and polymerization was performed at 135 ° C. and 1.33 kPa (10 mmHg) while circulating nitrogen. The colorless and transparent solid obtained was pulverized to obtain a powdery polymer (PML). The weight average molecular weight of the obtained PML measured by the above method was 3,500.

<Production Example 2> Production of lactic acid-aspartic acid copolymer (PAL) In a glass reactor of 500 ml size equipped with a stirrer and a degassing port, 39.9 g (0.3 mol of 0.3 mol of L-aspartic acid produced by Wako Pure Chemical Industries, Ltd. ), And 300.3 g (3.0 mol) of 90% L-lactic acid manufactured by Purac Co. were charged. The reactor was immersed in an oil bath, and dehydration polymerization was performed at 180 ° C. for 7 hours while circulating nitrogen. The obtained colorless transparent solid was pulverized to obtain a powdery polymer (PAL). The weight average molecular weight of the obtained PAL measured by the above method was 3,500.

<Comparative Example 1>
80 parts of polylactic acid (manufactured by Mitsui Chemicals, Inc., trade name "Racia H400", Mw = 240,000) and 20 parts of PML prepared in Production Example 1 are Labo Plastomill (manufactured by Toyo Seiki Seisakusho, Ltd., trade name " TOYOSEIKI, 4M150 ") was equipped with a segment mixer (manufactured by Toyo Seiki Seisakusho, Ltd., trade name" TOYOSEIKI, KF-70V2 ") and kneaded at 50 rpm and 175 ° C for 5 minutes. The obtained composition was hot pressed at 170 ° C. and rapidly cooled at 0 ° C. to obtain a press film 1. When the crystallinity was measured by the method described above, the crystallinity was 7.9%. The obtained film was subjected to a hydrolysis test by the method described above. The test results at each pH are shown in Tables 1 and 2.

<Comparative example 2>
A pressed film 2 was obtained in the same manner as in Comparative Example 1 except that the PML prepared in Production Example 2 was changed to PML, and the kneading temperature was 180 ° C. and the hot press temperature was 180 ° C. When the crystallinity was measured by the method described above, the crystallinity was 6.8%. The obtained film was subjected to a hydrolysis test by the method described above. The test results at each pH are shown in Tables 1 and 2.

<Example 1>
The press film 1 obtained in Comparative Example 1 was heat-treated under reduced pressure for 10 minutes at the crystallization temperature (105 ° C.) observed by the DSC measurement of Comparative Example 1 by hot pressing to crystallize the crystallized composition of the present invention. Item 1 was obtained. When the crystallinity was measured by the method described above, the crystallinity was 43.3%. The obtained film was subjected to a hydrolysis test by the method described above. The test results at each pH are shown in Tables 1 and 2.

<Example 2>
The press film 2 obtained in Comparative Example 2 was heat-treated under reduced pressure for 10 minutes by hot pressing at the crystallization temperature (110 ° C.) observed by the DSC measurement of Comparative Example 2 to obtain the crystallized composition 2 of the present invention. It was When the crystallinity was measured by the method described above, the crystallinity was 41.6%. The obtained film was subjected to a hydrolysis test by the method described above. The test results at each pH are shown in Tables 1 and 2.

<Comparative example 3>
Polylactic acid (manufactured by Mitsui Chemicals, Inc., trade name “Racia H400”) was hot pressed at 180 ° C. and rapidly cooled at 0 ° C. to obtain Press Film 3. When the crystallinity was measured by the method described above, the crystallinity was 1.9%.

<Comparative example 4>
Pressed film 3 obtained in Comparative Example 3 was heat-treated under reduced pressure for 1 hour at the crystallization temperature (120 ° C.) observed by the DSC measurement of Comparative Example 3 by hot pressing, and crystals containing no hydrolysis accelerator (B). A converted PLA film was obtained. When the crystallinity was measured by the method described above, the crystallinity was 52.1%.

It is clear from Tables 1 and 2 that the rate of weight loss is higher when the film is crystallized than when the film is quenched. In particular, it can be seen that polylactic acid can be completely decomposed in an extremely short time in spite of crystallization in an alkaline aqueous solution.
Usually, polylactic acid is slow to decompose when crystallized (Non-Patent Documents 1 and 2). Contrary to the conventional case, the crystallized composition of the present invention, when crystallized, accelerates the mass reduction due to decomposition. This is because the hydrolysis accelerator (B) according to the present invention is easily collected in the amorphous part by crystallization, and as a result, the acceleration of decomposition of the amorphous part is accelerated, thereby reducing the weight of the entire composition. It is believed that it accelerates and contributes to the collapse of the crystalline region.

The resin composition (C) according to the present invention is used for a molded product requiring an excellent decomposition rate, such as a film, a food packaging material, a packaging material for sanitary goods, an agricultural and horticultural material, a fiber, a nonwoven fabric, a sustained release drug, and the like. Applicable to Further, the hydrolysis method according to the present invention can easily and quickly hydrolyze the resin composition (C) according to the present invention by using a basic aqueous solution.
This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2016-211778 for which it applied on October 28, 2016, and takes in those the indications of all here.

Claims (8)

A resin composition comprising a crystalline polymer (A) composed of polylactic acid and a hydrolysis accelerator (B) composed of a copolymer of lactic acid and malic acid or aspartic acid , the crystal of the resin composition being A resin composition (C) having a degree of conversion of 15% or more and 55 % or less. The resin composition (C) according to claim 1, wherein a mass ratio of the crystalline polymer (A) and the hydrolysis accelerator (B) is 95/5 to 50/50. A crystalline polymer (A) containing a structural unit (a-1) derived from a hydroxycarboxylic acid and having hydrolyzability ;
A hydrolysis accelerator (B) containing a structural unit (a-2) derived from a hydroxycarboxylic acid and a structural unit (b-1) derived from a polyvalent carboxylic acid;
A resin composition (C) containing 15% or more and 55% or less of crystallinity of the resin composition in an aqueous solution having a pH of 8 or more. Characterized hydrolysis method. The hydrolysis method according to claim 3, wherein the temperature of the aqueous solution is 30 ° C or higher and lower than the melting point of the resin composition (C) . The hydrolysis method according to claim 3, wherein the crystalline polymer (A) is polyester . The hydrolysis method according to claim 3 or 4, wherein the crystalline polymer (A) is polylactic acid . The hydrolysis method according to any one of claims 3 to 6, wherein the mass ratio of the crystalline polymer (A) and the hydrolysis accelerator (B) is 95/5 to 50/50 . 8. The hydrolyzate according to claim 3, wherein the crystalline polymer (A) is polylactic acid, and the hydrolysis accelerator (B) is a copolymer of lactic acid and malic acid or aspartic acid. Disassembly method .